PROC. ENTOMOL. SOC. WASH. 96(4), 1994, pp. 757-763 PHYTOPHAGOUS INSECTS ASSOCIATED WITH BACCHARIS CONFERTA KUNTH AND B. DIOICA VAHL (ASTERACEAE: ASTEREAE) IN MEXICO W. A. Palmer and K. R. Pullen (WAP) Tropical Weeds Research Centre, Queensland Department of Lands, P.O. Box 187, Charters Towers, Queensland 4820, Australia; (KRP) 6 Dianella Road, Port Mac-quarie, N.S.W. 2444, Australia. Abstract. —SxxTvey^ of the phytophagous insect faunas on Baccharis conferta and B. dioica were undertaken in Mexico as part of a program to find biological control agents for B. haliinifolia. a serious weed in Australia. Fifty-three species were found on B. conferta but only eleven species on B. dioica. No species, from either plant, was considered a potentially valuable biological control agent for B. halimifolia. Key Words: surveys, biological control, Baccharis The woody shrub Baccharis halimifolia L. (Asteraceae: Astereae: Baccharidinae) is a declared noxious weed in Queensland, Australia, where it invades cattle pastures, reforested areas, and disturbed sites (Kleinschmidt and Johnson 1977, Stanley and Ross 1986). Native to the eastern sea-board of the United States (Stanley and Ross 1 986), it IS thought to have been introduced into Australia in the latter part of the 19th century (Bailey 1900). A biological control program has been supported by the Queens-land Department of Lands since 1960 as part of efforts to control this weed. The New World (and predominantly South American) genus Baccharis is ex-tremely large, with 450-500 species divided into a number of sections (Cuatrecasas 1967). More recently, Nesom (1990a) placed the 43 species native to North or Central America in six sections and placed B. hali-mifolia in the section Baccharis with 1 3 oth-er species. Host specificity work at the North Amer-ican Field Station over the past decade has indicated that most of the narrowly ste-nophagous insects found on B. halimifolia accept other species from the section Bac-charis as hosts in the laboratory (Palmer and Diatloff 1987, Palmer 1989, 19933, Palmer and Tomley 1993). Similarly, insects from these other species can attack B. halimifolia (Palmer and Tilden 1988, Palmer et al. 1993). Therefore any species placed in the section Baccharis is a potential source of biological control agents for B. halimifolia. This paper describes the insect fauna found in Mexico on two such species, B. conferta Kunth and B. dioica Vahl which were surveyed in an attempt to find more biological control agents for B. halimifolia. The Host Plants and THEIR Distribution Baccharis conferta is an erect shrub, up to 2 m in height, that resembles B. pilularis DC subspecies consanguinia in gross mor-phology. It occurs throughout central Mex-ico (Nesom 1990b) at altitudes greater than 2000 m. Baccharis dioica. also an erect shrub, grows to about 3 m in height. It very closely resembles B. halimifolia except that the leaves are not dentate. It occurs on the Yu-
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